An Auto-Calibration System for a Longitudinal Magnetic Recorder

Abstract

Multiple channel magnetic tape recording is often used for signal analysis of intelligence and telemetry data. To insure accuracy of the reproduced data, these systems require frequent calibration and alignment. As the number of tracks on these systems has increased, this task has become more time-consuming. Even with a well-trained technician, this task can take several hours at a minimum. To alleviate this problem, we developed a system for performing this calibration automatically. The implementation utilizes a Fast-Fourier-Transform technique to analyze the output of a pre-recorded signal on tape. The desired response, most frequently defined by IRIG Standards, is stored in a look-up table in the machine. The actual response is compared to that desired, and, under micro-processor control, adjustment made in the signal channel until an acceptable response is achieved. A unique photo-resistor technique is used in the signal path to control such parameters as gain and phase. A description of the hardware system will be given, as well as a description of the algorithms utilized for implementation.